Five per cent of the overall prison population are being set free on Christmas parole.

Justice Minister Alan Shatter has sanctioned the temporary release of 249 prisoners, which is the highest for several years but only marginally up on last year.

About three-quarters of those granted parole are serving their sentences in lower security institutions, such as the semi-open Training Unit and Loughan House and Shelton Abbey open centres.

The vast majority are already on incentivised regimes to encourage them to take part in structured activities.

The releases vary from a few hours, in some cases accompanied by a responsible person, to a maximum of seven nights and all are subject to stringent conditions. Offenders who break the conditions may be arrested and returned immediately to prison by the gardai.

The group includes Sean Courtney, who is completing a life sentence for the murder of Patricia O'Toole. He was convicted in January 1993 and is currently on a programme of regular temporary releases to prepare him for integration back into the community.

Courtney had admitted killing Ms O'Toole, an insurance company employee from Dublin, but claimed at his trial that he was insane at the time due to post traumatic stress disorder as a result of his experiences while serving with the Defence Forces in Lebanon.

High-profile figures who are not being let out for the Christmas period include Catherine Nevin; the so-called Scissors Sisters, Linda and Charlotte Mulhall; Eamonn Lillis; Joe O'Reilly; Brian Kearney and Warren Dumbrell.

Mr Shatter said that in addition to those being granted parole, some prisoners, who were very near the end of their sentences, were being granted full temporary release.

"Some other prisoners will also be facilitated with inter- prison visiting during the Christmas period," he added.

"The over-riding concern, when considering the applications, is the safety of the public.

"In addition to compassionate and humane considerations, other criteria taken into account include the nature and gravity of the offence, length of sentence served to date, prior record on temporary release, behaviour while in custody and previous criminal history," Mr Shatter said.

Last year, 226 inmates were set free, compared with 160 in 2011, 134 in 2010 and 176 in 2009.

Incentivised regimes were introduced last year on a phased basis across all prisons and inmates can benefit from extra telephone calls, an increased amount and duration of visits and different levels of gratuity.